1. Field of the Invention
The present invention relates to systems and methods for sorting objects (e.g., parcels or other objects)
2. Discussion of the Background
There are numerous organizations that sort objects by some object attribute (e.g., purchase order, stock number, destination point or any number of other attributes of the object). In many cases, the sorting machines involved do not have enough sorting fidelity (e.g., number of outputs) to provide 100% sorting capacity within a single sorting process. Typically, this is addressed through the creation of primary and secondary sort plans designed to create one level of separation on the primary sort and then a finer degree of separation on the secondary sort(s).
In some cases, such as mail processing, matched sort plans are used to sequence the mail into a specific order such as the delivery sequence of the mail carrier. Typically, these are two, or three pass sorting operations.
Because it may take more than one sort to separate, or sequence, objects to the desired level of separation it is important that the base throughput of the sorting machinery be as high as possible to offset the time consumed in performing multiple passes, or sorts. For example, if a system operates at 30,000 objects per hour and must perform two sorts to create the sort fidelity required, then the operational throughput of the sorting process can be no better than 15,000 objects per hour (set up time, system sweeping and other ‘overhead functions’ degrade this further).
There are some sorting systems that are configured to produce throughputs higher than the base system with a simplified configuration (see e.g., U.S. Pat. No. 6,889,814). Usually, systems of this type have a continuous loop conveyor that has a first feeder (or “induction station”) located at one “end” of the conveyor and a second feeder located at the opposite “end” of the conveyor. The feeders feed objects onto the conveyor, and the objects are then conveyed to an output section (or “discharge station”) that is associated with the object. By feeding objects into the system at opposite ends of the system, the system has multiple opportunities to use the sorting mechanism (e.g., tilt tray, cross belt, carousel, or other sorting mechanism) as some of the objects are loaded at one end and sorted prior to reaching the second feeder allowing for an average of more than one sort per cycle of the carrying mechanism.
Configuring the sort plan such that the high volume sort locations are on one side of the machine can enable even higher utilization for the second set of feeders. Unfortunately, these types of system have limitations that are driven by the random nature of the material being presented to the feeders.
Ideally, one would like to process such a system at the theoretical maximum possible throughput (e.g., twice the base throughput for a system using two sets of feeders). In doing so, the system would be run at the maximum possible efficiency, operating at half the speed of a single feeder system and producing the same throughput. The capability to operate at slower processing speeds reduces the number of errors introduced into the process and minimizes potential damage to the product.